A) Field of the Invention
The present invention relates to a light emitting device and a method for manufacturing the light emitting device.
B) Description of the Related Art
FIG. 12 is a schematic sectional view illustrating a semiconductor light emitting device of the related art. A light emitting device is used as, for example, a light source of a vehicle illumination device such as a vehicle headlight. In the light emitting device illustrated in FIG. 12, a plurality of light emitting diode (LED) elements 54 are mounted on a substrate 51 made of, for example, silicon (Si).
Each of the LED elements 54 includes a support substrate 54b and a semiconductor layer 54a that is disposed on the support substrate 54b. The semiconductor layer 54a includes, for example, an n-type semiconductor layer, an active layer (light emitting layer), and a p-type semiconductor layer. An n-side electrode is electrically connected to the n-type semiconductor layer, and a p-side electrode is electrically connected to the p-type semiconductor layer. An example of each of the LED elements 54 is a nitride-based semiconductor light-emitting element that emits blue light.
The LED elements 54 are bonded to corresponding metal patterns 52, which are disposed on the Si substrate 51, with corresponding bonding layers 53 interposed therebetween. The LED elements 54 can be driven independently of one another, that is, independent control of the LED elements 54 in a light-emitting state and in a non-light-emitting state can be performed by a driving signal (power) supplied by a driving circuit via the metal patterns 52.
A fluorescent layer 55 is disposed on the LED elements 54. The fluorescent layer 55 includes, for example, fluorescent particles that emit yellow light. The blue light that is emitted by the LED elements 54 and that is incident on the fluorescent particles of the fluorescent layer 55 is converted into yellow light by wavelength conversion. The yellow light obtained by the wavelength conversion and the blue light that was not incident on the fluorescent particles are emitted from the fluorescent layer 55 and visually recognized as white light.
In the light emitting device illustrated in FIG. 12, regions between the LED elements 54 are non-light-emitting regions, and thus, when two of the LED elements 54 that are adjacent to each other are turned on, a dark portion is formed in the region (non-light-emitting region) between the two LED elements 54. For example, in the case where the plurality of LED elements 54 are arranged in a matrix and where all the LED elements 54 are turned on, a dark portion is formed in lines or in a grid-like pattern, and accordingly, a problem occurs in that a uniform illumination pattern cannot be formed in a vehicle headlight.
In addition, for example, in the case where two of the LED elements 54 are adjacent to each other, one of the two LED elements 54 being turned on, and the other one of the two LED elements 54 being turned off, light emitted from the one of the two LED elements 54, which is turned on, is propagated to a region in which light is not turned on through the fluorescent layer 55, which in turn results in cross talk. Cross talk is a phenomenon in which light appears to be emitted at a position at which no LED element is disposed or at a position at which an LED element that is turned off is disposed. A problem occurs in that this cross talk makes it difficult to obtain a good contrast.
There is known a technology for arranging a light blocking object between LED elements in order to suppress the occurrence of cross talk (see, for example, Japanese Unexamined Patent Application Publication No. 2010-87224 and Japanese Patent No. 3941487). However, in order to arrange such a light blocking object, it is necessary to increase the gap between LED elements. As a result, the luminance between the LED elements is reduced, and consequently, a notable dark portion will be formed between the LED elements that are turned on.
As described above, it is difficult to realize both a reduction in the area of a dark portion and a reduction in the probability of the occurrence of cross talk.
A light emitting device that includes a light blocking portion in a fluorescent layer has been disclosed (see, for example, Japanese Unexamined Patent Application Publication Nos. 2014-197690 and 2014-220295).
In the invention described in Japanese Unexamined Patent Application Publication No. 2014-197690, a plurality of light blocking portions and portions of a fluorescent layer are integrally formed and mounted on an array of LED elements, or a plurality of members that are combinations of portions of a fluorescent layer and light blocking portions are formed and mounted on an array of LED elements.
The fluorescent layer described in Japanese Unexamined Patent Application Publication No. 2014-220295 includes, for example, fluorescent portions of the three primary colors, which are red, green, and blue (RGB) and whitish partition portions that are disposed between the fluorescent portions, and color rendering effect can be obtained.